Protons are positively charged particles found in the nucleus of an atom. Electrons are negatively charged, neutrons are neutral, and photons are particles of light, not constituents of atomic charge.

The atomic number is defined as the number of protons in an atom's nucleus, which uniquely identifies the element. Neutron count and electron number (in neutral atoms) are determined separately.

The mass number is determined by adding the protons and neutrons together in the nucleus of an atom. Electrons contribute very little mass and are not included in this calculation.

The Bohr Model introduces the concept of electrons orbiting the nucleus in fixed, quantized energy levels. This model was instrumental in explaining the line spectra of atoms.

Rutherford's Gold Foil Experiment revealed that a small fraction of alpha particles were deflected at large angles, indicating the presence of a concentrated, positively charged nucleus. This finding contradicted earlier, more uniform models of atomic structure.

J.J. Thomson proposed the plum pudding model, which described the atom as a positively charged sphere with electrons embedded throughout. This model was later replaced as new experimental evidence emerged.

Bohr's Model was revolutionary in incorporating the idea that electrons exist in discrete energy levels. This quantization helps explain the observed atomic emission spectra.

The fact that most alpha particles passed through the foil implies that atoms are primarily empty space. The few deflections indicated the presence of a small, dense, positively charged nucleus.

The mass number (24) minus the atomic number (10) gives the number of neutrons: 24 - 10 = 14. This basic calculation is essential for understanding isotopic composition.

The bottom number in nuclear notation signifies the atomic number, which determines the number of protons in an atom's nucleus. This is a fundamental property that defines the element.

Isotopes are forms of the same element that have identical numbers of protons but vary in their neutron count. This difference leads to variations in mass while maintaining the same chemical properties.

Discrete emission lines occur when electrons jump from one quantized energy level to another, releasing energy in the form of light at specific wavelengths. This phenomenon is a central feature of the Bohr model.

Atomic mass on the periodic table is a weighted average of the masses of an element's naturally occurring isotopes. This value reflects both the mass and the abundance of each isotope.

The Quantum Mechanical Model describes electrons in terms of probability clouds or orbitals, effectively capturing their wave-particle duality. This model offers a more complete picture of electron behavior than earlier models.

Thomson's work with cathode rays provided evidence for the existence of the electron. His experiments fundamentally altered the understanding of atomic structure.

The atomic number (bottom number) is 7, which means there are 7 protons and, in a neutral atom, 7 electrons. The number of neutrons is calculated by subtracting the atomic number from the mass number: 15 - 7 = 8.

The Quantum Mechanical Model describes electron positions in terms of probabilities, forming orbitals or electron clouds rather than fixed paths. This model better accounts for the behavior of electrons in more complex atoms.

Rutherford's gold foil experiment revealed that a small, dense nucleus accounts for most of the atom's positive charge. This finding directly contradicted Thomson's model, which proposed a diffuse, uniform distribution of charge.

Isotopes of an element share the same atomic number, meaning they have the same number of protons. The differences in isotope identity arise from variation in the number of neutrons.

Bohr's model successfully explains the hydrogen emission spectrum but fails to extend to more complex atoms. The quantum mechanical model, with its probabilistic electron orbitals, offers a more accurate and comprehensive representation of electron behavior.